Britain’s spy agency GCHQ has secretly gained access to the network of cables which carry the world’s phone calls and internet traffic and has started to process vast streams of sensitive personal information which it is sharing with its American partner, the National Security Agency (NSA).

The sheer scale of the agency’s ambition is reflected in the titles of its two principal components: Mastering the Internet and Global Telecoms Exploitation, aimed at scooping up as much online and telephone traffic as possible. This is all being carried out without any form of public acknowledgement or debate.

One key innovation has been GCHQ’s ability to tap into and store huge volumes of data drawn from fibre-optic cables for up to 30 days so that it can be sifted and analysed. That operation, codenamed Tempora, has been running for some 18 months.

GCHQ and the NSA are consequently able to access and process vast quantities of communications between entirely innocent people, as well as targeted suspects.